An acceleration sensor, a gyroscope, a displacement sensor, a pressure sensor, or other type of physical quantity sensor for detecting a physical quantity change as a capacitance change, is required to ensure insulation resistance and reduce circuit noise when a capacitance detection circuit thereof needs to have a high resolution or when a MEMS (Micro Electro Mechanical System) sensor needs to be combined with the capacitance detection circuit in order to achieve cost/size reduction.
The prior art of Patent Document 1 (identified further on), therefore, describes a method for manufacturing a printed circuit board, which does not require a solder resist with a hygroscopic solder mask and prevents solder from flowing in a component mounting section, by implanting a metal conductor layer into a surface of an insulating substrate containing at least an organic resin, and then etching a surface of the metal conductor layer onto which, for example, a terminal of an electronic component is soldered, to form a concave portion that is 0.5 to 30 μm deep from the surface of the insulating substrate.
Furthermore, in order to provide a resist ink composition in which deterioration of the electrical characteristics such as insulation resistances does not occur even under high humidity, and to provide a printed wiring board having a cured film of the resist ink composition, the prior art described in Patent Document 2 (identified further on) suggests a printed wiring board that has a solder-resist ink plastic substance and a film for covering the solder resist ink composition, the solder-resist ink composition containing a colorant, hardening resin, reactive diluent, polymerization initiator, and filler.
Patent Document 1: Japanese Patent Application Publication No. H10-173296
Patent Document 2: Japanese Patent Application Publication No. 2003-98660
However, the problem pertaining to the prior art described in Patent Document 1 is that the structure of the printed circuit board is complicated because the surface of the metal conductor layer, implanted into the surface of the insulating substrate and having a terminal of an electronic component soldered thereto, is etched into a concave that is 0.5 to 30 μm deep from the surface of the insulating substrate.
The problem pertaining to the prior art described in Patent Document 2 is that solder-resist ink with a special composition needs to be used, which increases the production cost.